Quote:
Originally Posted by 3002 tii
I wonder if that’s intentional and what causes the echo when switching over to blue bus
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The two front speakers are what the TCU uses. This is a carryover from the E31 / E32 / E34 / E36 and early E38 & E39 where the phone module directly drove a secondary coil on the front speakers for call audio. To cut down on wiring, newer E-chassis switched to a system where the call audio would come from the TCU over to the radio, and the radio would switch the front speakers on using existing wiring.
Some E46s had a speaker under the steering column for call audio, but that was only there until 2001.
The echo is likely attributed to the fact that the newer 762 microphone is over gained (which is why BMW touted it as noise cancelling -- the added gain allowed them to more easily apply a NR algo). As I mentioned, not everyone has the issue, and the 338 microphone doesn't have the issue whatsoever.
-Ted